Cathode for an organic electronics component

ABSTRACT

A metal cathode layer manufactured from a low-melting alloy for an electronic component is described.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part and claims the benefit of priority under 35 U.S.C. Section 120 of International Application Serial No. PCT/EP2004/000427, filed Jan. 20, 2004, which claims priority to German Application Serial No. 103 02 143.4, filed Jan. 21, 2003. The disclosures of the prior applications are considered part of and are incorporated by reference in the disclosure of this application.

BACKGROUND

The invention relates to a novel metal cathode layer for an electronic component, especially for an organic light emitting diode (OLED), as well as a manufacturing procedure for said cathode.

Cathodes are known for OLEDs that usually consist of a two-layered stack. The first layer is usually made of two types of materials. Either the first layer is made of rather reactive metals, such as barium or calcium, or insulating substances, such as cesium fluoride or lithium fluoride. The second layer is typically made of a more-or-less precious metal, such as silver or aluminum, and serves as an electrode path and to protect the inner layers from oxidizing gases. The two layers are conventionally manufactured with a water partial pressure and oxygen partial pressure below 10⁻⁹, i.e., in an ultravacuum. These conditions can be created by a genuine ultrahigh vacuum pump or in an inert gas atmosphere at a pressure below 10⁻⁶. This inert gas pressure then has a water partial pressure and oxygen partial pressure below the limit that would damage the OLED structure. Both manufacturing processes are clearly very expensive and not that efficient.

The task of the present invention is therefore to create a cathode for an electronic component, especially for an organic light emitting diode, that can be manufactured without an ultrahigh vacuum.

SUMMARY

The subject of the invention is a cathode for an organic electronic component that includes a metal alloy applied at least in part in a molten state. In addition, the subject of the invention is a method to manufacture a cathode for an OLED by applying the molten metal alloy.

In one aspect, the invention is directed to an organic electronic component comprising a cathode manufactured from a molten metal alloy.

Implementations of the invention can include a component with an alloy that is molten at temperatures ranging from 30 to 200° C. The alloy can be insensitive to oxidation. The alloy can be insensitive to oxidation when molten. The alloy can include cadmium, tin, bismuth, lead, indium, mercury or silver. The alloy can include both tin and indium or tin and bismuth. The alloy can be a eutectic alloy. The alloy can include a wetting agent and an adhesion promoter.

In another aspect, the invention is directed to a method of manufacturing a device, wherein a molten metal alloy forms a cathode of an electronic component.

Implementations of the invention can include applying the molten metal alloy with a printing process. The molten metal alloy can be applied in an unstructured manner. The method can further include depositing a powder. The method can also include applying a fusible alloy with an embossing technique to form a cathode of an electrical component. The molten metal alloy can be applied over one or more organic layers.

Aspects of the invention can include none, one or more of the following advantages. The low-melting alloys may produce a homogenous film with a low flaw rate in contrast to films that are manufactured by means of PVD. Conventional cathodes manufactured by PVD can have a high flaw rate, which can be a reason for the degradation of the OLED from an increasing amount of dark spots. The manufacturing procedure using molten metal alloys to form a cathode is not limited to hard substrates; it can be applied to flexible substrates. Even at a thickness of about 1 mm, the low-melting metal alloy may be flexible. The cathode can be used with organic light emitting devices, organic detectors, integrated circuits, organic solar cells or photovoltaic cells.

The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view of an organic light emitting device.

DETAILED DESCRIPTION

Due to the high melting point of metals or typical alloys (far above 200° C.), application techniques other than physical vapor deposition (PVD) cannot be used to manufacture a cathode, because temperatures above approximately 130 to 150° C. significantly damage the emitter material (depending on the polymer). However, there is a class of metal alloys, the so-called fusible alloys, that are distinguished by low melting points ranging from 30 to 200° C. Typically, the melting point of the alloy is lower than that of the metals from which the alloy is made. These metal alloys therefore allow cathodes to be manufactured from the molten material at temperatures that an emitter material can tolerate. There is a whole series of commercially available fusible alloys that can all be used for manufacturing cathodes.

The metal alloy for manufacturing the cathode is preferably insensitive to oxidation, especially above its melting temperature, so that inert gas atmospheres are not required to apply the molten material.

In one embodiment of the method, the molten material is applied preferably in a structured manner by a printing process, such as stamp printing, pad printing, serigraphy, inkjet printing, and relief printing, intaglio printing, screen printing, flexographic printing, etc.

According to another embodiment of the method, the fusible alloy is applied by means of an embossing technique, or like a cast resin.

The molten material can also be applied in an unstructured manner just as well by spin coating, dipping, a doctor blade, etc., and the alloy material can even be structured in a later production step.

The fusible alloys are known according to their type. They are, for example, alloys that form a eutectic layer; that is, when the components in the alloy reach a specific percentage molar distribution, weight distribution or volume distribution, the melting point of the alloy or mixture falls far below that of the individual components. Another advantage of eutectic alloys is that they have a specific melting point in contrast to a melting range of 10° C. or more in certain circumstances.

The alloy is preferably molten between 30° C. and 200° C., such as below 150° C.

The following metals can be components of these alloys: bismuth, lead, tin, cadmium, indium, mercury, and silver. The fusible alloy is distinguished in that the melting point lies far below that of individual components measurable in degrees Celsius.

Fusible alloys not hazardous to health are can be used, i.e., alloys that require little or no cadmium, mercury and/or lead. The following alloys can be cited as examples: 57% (weight percent) bismuth, 17% tin, 26% indium (melting point 78° C.); 48% tin, 52% indium (melting point 118° C.) or 58 percent bismuth, 42% tin (melting point 138° C.).

The alloy can include (conventional) additives such as wetting agents, adhesion promoters, or the like.

A major advantage of the method is also that these materials produce a homogenous film with a low flaw rate in contrast to films that are manufactured by means of PVD. Conventional cathodes manufactured by PVD can have a high flaw rate, which is the main reason for the degradation of the OLED from an increasing amount of dark spots.

The method according to the invention to manufacture cathodes can be used to produce thin films that are flexible enough for flexible applications.

Referring to FIG. 1, to manufacture a passive matrix display based on light-emitting polymers, familiar manufacturing techniques are used for forming layers on a substrate 1, such as a glass substrate, up to the cathode 4. The layers can include an anode 2, one or more organic functional layers 3 and bond pads 5 for contacting the anode 2 and cathode 4. The first cathode layer, for example the injection layer consisting of insulated material, can be deposited in the form of a powder. Then the outer cathode layer of fusible alloys can be printed, for example, at a thickness of 200 to 500 micrometers. The fusible alloys can be printed while in a molten state. The molten material is allowed to cool and harden. Additional processing steps can be performed to complete the device, such as encapsulation or bonding a cap 6 to encapsulate the device. This manufacturing procedure is not limited to hard substrates; it can easily be applied to flexible substrates.

This is of particular relevance to flexible light sources; it should be noted that tests have shown that thin layers (<1 mm) of fusible alloys are almost flexible.

Likewise, organic solar cells or photovoltaic cells can also include a cathode described above, including cells on a flexible substrate. The same holds true for flexible organic detectors and integrated circuits.

The cathodes described above can be used for all types of organic electronic components.

A number of embodiments of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims. 

1. An organic electronic component comprising a cathode manufactured from a molten metal alloy.
 2. The organic electronic component according to claim 1 wherein the alloy is molten at temperatures ranging from 30 to 200° C.
 3. The organic electronic component according to claim 1, wherein the metal alloy is insensitive to oxidation.
 4. The organic electronic component according to claim 3, wherein the metal alloy is insensitive to oxidation when molten.
 5. The organic electronic component according to claim 1, wherein the metal alloy contains at least one metal selected from the group consisting of cadmium, tin, bismuth, lead, indium, mercury and silver.
 6. The organic electronic component according to claim 1, wherein the metal alloy includes tin and indium.
 7. The organic electronic component according to claim 1, wherein the metal alloy includes tin and bismuth.
 8. The organic electronic component according to claim 1, wherein the metal alloy is a eutectic alloy.
 9. The organic electronic component according to claim 1, wherein the metal alloy includes a wetting agent.
 10. The organic electronic component according to claim 1, wherein the metal alloy includes an adhesion promoter.
 11. A method of manufacturing a device, comprising applying a molten metal alloy to form a cathode of an electronic component.
 12. The method according to claim 11, wherein applying the molten metal alloy includes a printing process.
 13. The method according to claim 11, wherein applying the molten metal alloy includes applying the molten metal alloy in an unstructured manner.
 14. The method of claim 11, further comprising depositing a powder.
 15. The method of claim 11, wherein applying a molten metal alloy to form a cathode includes applying the molten metal over one or more organic layers.
 16. A method of manufacturing a device, comprising applying a fusible alloy with an embossing technique to form a cathode of an electrical component. 